NO321914B1 - Fluorescent compounds for use in industrial water systems - Google Patents

Abstract

Fluorescent compounds of the formula:wherein R1 and R2 are either both SO3M, or one of R1 and R2 is SO3M and the other is COOM, where M is selected from the group consisting of H, Na, K, Rb, Cs, Li or ammonium, are described and claimed. These inert flurorescent compounds have been found to be resistant to oxidizing biocides. One process for making these compounds is described and claimed as the condensation between a 1,8-naphthalic anhydride possessing the desired functionalities and the appropriately substituted o-phenylene diamine. Alternatively, o-amino-nitro-aromatics may be condensed with the various 1,8-naphthalic anhydrides when the in situ reduction of the nitro group is accomplished with a suitable reducing agent such as iron powder. The resulting fluorescent compounds can be used as inert fluorescent tracers in industrial water systems.

Description

The present invention relates to fluorescent compounds. In one embodiment, it deals with fluorescent compounds that have been synthesized and subjected to stability testing for use as inert tracers in industrial water systems. In another embodiment of the present invention, alternative processes are provided for the production of fluorescent compounds.

The background of the invention

The use of an inert fluorescent compound to trace the hydraulic losses and gains from an industrial water system has been known since the late 1980s.

Industrial water systems are very numerous. A typical industrial water system is a cooling tower where water is used in a heat exchanger role. To optimize application of treatment agents in such systems and to ensure that overall appropriate hydraulic conditions are maintained in the system, it is advantageous to determine the amount of treatment agent added to the system according to recommended application levels specific to the environment. If there is an undertreatment of treatment agent, deposition of "deposition" (scaling) salts and corrosion can quickly occur. If there is an over-processing of treatment agent, treatment agent will be played with a corresponding monetary loss.

The continuous monitoring in operation of the amount of treatment agent added to a moving body of water through the use of a tracer comprising an inert fluorescent compound is an established practice as described in U.S. Patent Numbers 4,783,314 and 4,992,380. These patents contain background information that does not need to be repeated here, but their contents are incorporated herein by reference.

To be useful in such systems, the fluorescent compound used must be non-consumable or systemized. There are certain known compounds that are in

capable of acting as inert fluorescent tracers, however, there is no large number of such compounds. •Therefore, there is a continuous need to develop additional inert fluorescent tracer compounds that are capable of working in aqueous systems, especially where such systems contain oxidizing biocides.

Summary of the invention

The first embodiment of the present invention is a fluorescent compound of the formula:

wherein R 1 and R 2 are either both SO 3 M or one of R 1 and R 2 is SO 3 M and the other a COOM, wherein M is selected from the group consisting of H, Na, K, Rb, Cs, Li or ammonium.

The second embodiment of the present invention is a method for producing a fluorescent compound having the formula:

wherein R 1 and R 2 are as previously defined, which comprises condensing a 1,8-naphthalic anhydride of the formula: with an o-phenylene diamine of the formula:

where Ri and R2 are as previously defined.

The third embodiment of the present invention is a method for producing fluorescent compounds of formula I:

by condensing o-amino-nitroaromatics of the formula where Ri is as previously defined, with the appropriate 1,8-naphthalic anhydride:

where R2 is as previously defined,

wherein such condensation is carried out in such a way that in situ reduction of the nitro group is carried out with a suitable reducing agent.

The fourth embodiment of the present invention is the use of a compound with the formula:

where Ri and R2 are as previously defined, as an industrial tracer in an industrial water system.

Detailed description of the invention

The present invention is based on the discovery of certain naphthalimide-based compounds. These naphthalimide-based compounds are not only fluorescent, but are also stable in the presence of oxidizing biocides such as bleach, bromine, stabilized chlorine and stabilized bromine. Therefore, these particular naphthalimide-based compounds are particularly useful as inert fluorescent tracers in industrial water systems containing bleach and/or stabilized bromine.

These particular naphthalimide-based compounds can be readily prepared through the condensation of a 1,8-naphthalic anhydride having the appropriate functionalities with the appropriately substituted o-phenylene diamine. They can also be prepared by the condensation of a 1,8-naphthalic anhydride having the appropriate functionalities with an o-amino-nitro aromatic in the presence of a suitable reducing agent.

The fluorescent compounds according to the present invention are naphthalimide-based compounds with the following structure:

wherein R 1 and R 2 are either both SO 3 M, or one of R x and R 2 is SO 3 M and the other is COOM, wherein M is selected from the group consisting of H, Nam K, Rb, Cs, Li or ammonium.

The fluorescent compounds according to the present invention can conveniently be prepared by a one-step condensation between a 1,8-naphthalic anhydride which has the desired functionalities and the suitably substituted o-phenylene diamine. Suitable 1,8-naphthalic anhydrides for the preparation of the fluorescent compounds according to the present invention are those selected from the group with the formula:

in which R2 is as previously defined. When R 2 is SO 3 K, then compound II is 4-sulfo-1,8-naphthalic anhydride, potassium salt, and compound II is available from Aldrich Chemical Company, P.O. Box. 2060, Milwaukee, WI 53201 USA; Telephone numbers (414)273-3850 and (800)558-9160.

Similarly, suitable o-phenylene diamine compounds useful in the preparation of the fluorescent compounds of the present invention are those of the formula:

in which Ri is as previously defined. When R1 is COOH, then

compound III 3,4-diaminobenzoic acid and compound III are available from Aldrich. When R 1 is SO 3 H, then compound III is 3,4-diaminobenzenesulfonic acid and compound III is available from Bayer AG, Organic Chemicals Business Group, Marketing, Leverkusen, D-51368, Germany, telephone number: +49 214 30-8514.

In a currently preferred embodiment of the present invention, the fluorescent compounds can be prepared in a one-step condensation between an appropriately substituted naphthalic anhydride and an appropriately substituted o-phenylene diamine.

Alternatively, o-amino nitro aromatics with the formula can

where Ri is as previously defined, is condensed with the appropriate 1,8-naphthalic anhydride when such condensation is carried out in such a way that in situ reduction of the nitro group is carried out with a suitable reducing agent such as, but not limited to, iron powder. When Ri is SO 3 M then compound IV is o-nitroaniline-p-sulfonic acid (and salts thereof) and compound IV is available from Bayer AG. When R 1 is COOH, Compound IV is 4-amino-3-nitro-benzoic acid, and Compound IV is available from ACROS Organics, a division of Fisher Scientific, 600 Business Center Drive, Pittsburgh PA 15205, telephone number 1-800-227-6701 . When Rx is SO3M then compound IV is 2-nitroaniline-4-sulfonic acid and its salts and compound IV is available from TCI

America, 9211 North Harborgate Street, Portland OR 97203, telephone number 800-423-8616.

Fluorescence is defined as the re-emission of photons (energy) with a longer wavelength (lower frequency) by a molecule that has absorbed photons (light) with shorter wavelengths (higher frequency). Both absorption and emission (emission) of energy are unique characteristics of a particular molecule (structure) during the fluorescence process. Light is absorbed by molecules and causes electrons to be excited to a higher electron state. The electrons remain in the excited state for about 10~<8> seconds, then, assuming that all the excess energy is not lost by collisions with other molecules, the electron returns to the ground state. Energy is emitted during the electrons' return to the ground state. The Stokes shift is the difference in wavelength between absorbed and emitted light. The emitted wavelength is always longer than or equal to the incident wavelength, due to energy conservation; the difference is absorbed as heat in the material's atomic lattice structure.

When their fluorescent properties were tested, the present claimed compounds were found to have a fluorescent signal excitation energy value above 380 nm. Consequently, these compounds have a different fluorescent signal than Nalco Chemical Company's inert tracer 1,3,6,8-pyrene tetrasulfonic acid tetrasodium salt (PTSA). PTSA is available from Nalco Chemical Company, One Nalco Center, Naperville, IL 60563, telephone number (630)305-1000. Accordingly, the present inert tracers can be used together with PTSA for monitoring and control purposes in an industrial water system, because their fluorescent signal does not overlap with that of PTSA.

The inert fluorescent compounds according to the present invention exhibit excitation and emission maxima in the range of 385-400 nm and 510-530 nm, respectively. This wide spectral operating range, provided by the compounds of the present invention, will improve the applicability of these compounds as inert fluorescent tracers. In addition, the large difference between the excitation and emission maxima (called the Stokes shift) may serve to minimize interference due to background hydrocarbons, since very few species have a Stokes shift that large.

The fluorescent compounds according to the present invention can be used in any industrial water system where an inert tracer is required. Examples of such systems are cooling tower water systems (including open recirculation, closed and once-through systems); petroleum wells, downhole formations, geometric wells and other oilfield applications; steam boilers and steam boiler water systems; mineral process water including mineral washing, flotation and beneficiation; paper mill boilers, washing plant bleaching plants and waste water systems; black liquor evaporators in the cellulose industry; gas scrubbers and air scrubbers; continuous casting processes in the metallurgical industry; air conditioning and refrigeration systems; industrial and petroleum process water, indirect contact cooling and heating water, such as pasteurization water, water recycling and purification systems; membrane filtration water cisterns; food processing streams (meat, vegetables, sugar beet, sugar cane, grain, poultry and soybean); and waste treatment systems as well as clarifiers, liquid-solid applications, public sewage treatment and industrial or public water systems.

When using the fluorescent compounds according to the present invention as inert tracers in industrial water systems, it is generally desirable to use the smallest amount of fluorescent compound that is practical for the circumstances. It is of course understood that the amount of the fluorescent compound added to the water system must be at least an amount sufficient for the fluorescent signal measurements to be made. In general, the system concentration of an inert fluorescent compound at the sampling location in the water system should be at least about 0.01 ppb and no more than about 10 ppm. Preferably, the concentration of fluorescent compound is between about 50 ppb and about 500 ppb. Most preferably, the concentration of fluorescent compound is between about 100 ppb and 400 ppb. Of course, it is possible to add more than 10 ppm of the inert fluorescent compound to the water system and detect the compound's fluorescent signal, but using any amount of inert fluorescent compound above 10 ppm is an unnecessary waste of inert fluorescent compound.

The meaning of the term "inert", as used herein, is that an inert fluorescent tracer is not appreciably or significantly affected by any other chemistry in the system, or by the other system parameters such as metallurgical composition, microbiological activity, biocide concentration, heat changes or total heat content . To quantify what is meant by "not appreciably or significantly affected", this statement means that an inert fluorescent compound has no more than a 10% change in its fluorescent signal under conditions normally encountered in industrial water systems. Conditions commonly encountered in industrial water systems are known to those of ordinary skill in the art of industrial water systems.

Of course, it is possible to cause a greater than 10% change in the fluorescent signal by subjecting the fluorescent compound to stress that is not normal for an industrial water system. For example, the fluorescent signal of one of the present claimed compounds (disulfonaphthalimide or DSN) will change more than 10% if the compound encounters more than 42,000 ppm pyrophosphate (as PO4), or if it encounters more than 34,000 ppm sodium (as Na+) . The fluorescent signal of another of the present claimed compounds (carboxysulfonaphthalimide or CSN) will change more than 10% if the compound encounters more than 3100 silicates (as SiC>2), or if it encounters more than 41000 ppm sodium (as Na+).

The present claimed compounds have been found to remain inert when encountering the standard components of industrial water systems. However, it has also been found that the inertness of the present demanding compounds can be challenged by a change in pH. The DSN compound has been found to be inert over a pH range of from about 2 to about 9 and the CSN compound has been found to be inert over a pH range of from about 5 to about 10. When operating the water system within these pH ranges , both DSN and CSN have been found to be effective inert fluorescent tracers.

An advantage provided by the fluorescent compounds of the invention is that they have been found to be inert to the degrading effects of oxidizing biocides. Therefore, they are particularly useful in systems that use oxidizing biocide(s) to minimize microbial activity.

Examples

The following examples are intended to be illustrative of the present invention and to show the person skilled in making and using the invention. These examples are not intended to limit the invention in any way.

Example I

Preparation of Disulfonaphthalimide (DSN)

where R 1 is SO 3 Na and R 2 is SO 3 K

A 100 ml round bottom flask was charged with 3.16 parts of 4-sulfo-1,8-naphthalic anhydride, potassium salt; 2.40 parts of 3-nitro-4-aminobenzenesulfonic acid, sodium salt; 1 part iron powder and 30 parts glacial acetic acid. The mixture was refluxed with vigorous stirring for 6 hours. After cooling, the orange/yellowish solid was collected by filtration, washed with deionized water and isopropanol, and dried in vacuo to give 4.21 parts of the title compound. This material was further purified by stirring 4 parts of the crude solid in 100 parts of boiling methanol and filtering the hot suspension. Accordingly, 3.65 parts of a dark yellow compound were obtained after drying in vacuo.

Example II

Preparation of carboxysulfonaphthalimide (CSN)

where R 1 is COOH (converted to COOK using potassium carbonate), and R 2 is SO 3 K.

A 100 ml round bottom flask was charged with 3.16 parts of 4-sulfo-1,8-naphthalic anhydride, potassium salt; 1.55 parts 3,4-diaminobenzoic acid, and 30 parts glacial acetic acid. The mixture was refluxed with vigorous stirring for 6 hours; whereby, the appearance of the suspension was changed from a light brown color to a faint yellow color. After cooling, the yellow solid was collected by filtration, washed with deionized water, and dried in vacuo to give 4.10 parts of the title compound.

An aqueous solution of CSN can be made by taking 1 part of the title compound, suspending it in 100 parts of deionized water, and keeping the pH of the solution slightly alkaline via the addition of potassium carbonate.

Example III

Oxidative biocidal stability of the compounds of Formula I

The test of oxidizing biocide stability was carried out in the following way. Solutions of simulated water were prepared with the desired levels of cations and anions at the desired pH. For these experiments, the simulated cooling water contained 360 ppm Ca (as CaCO 3 ), 200 ppm Mg (as CaCO 3 ), 300 ppm alkalinity (as CaCO 3 ), and 15 ppm phosphonate to prevent CaCC>3 precipitation. The water was then adjusted to the desired pH with HCl or NaOH. The tests were carried out at pH 9.

A series of three amber bottles were labeled with the desired test sample. 25 ml of the simulated water was delivered to each of the three labeled bottles. One of the bottles (marked B) was supplied with 30 µl of a 1200 ppm bleach solution. To a second bottle (labeled S) was supplied 30 µl of a 1200 ppm working solution of a liquid stabilized bromine solution available as STA-BR-EX™ from Nalco Chemical Company. The third bottle (marked N) was supplied with 30 µl of distilled water.

The amount of free and total chlorine was measured immediately after the samples were prepared and 24 hours later at the time of fluorescence analysis. The bottles were stored for 24 hours in the dark. After 24 hours, fluorescence measurements were made using the sample labeled N as the reference sample. % fluorescence consumed in the presence of an oxidizing biocide was calculated as shown below.

Oxidative biocide stability data are presented in Table I. For comparison, known inert fluorescent tracers were: l-methoxypyrene-3,6,8-trisulfonic acid trisodium salt (available from Molecular Probes, 4849 Pitchford Avenue, Eugene, Oregon 97402, telephone number (541)465- 8300) and pyrene-1,3,6,8-tetrasulfonic acid tetrasodium salt (PTSA) included.

When reading the data in the table, the lower the amount (% consumed) of fluorescence consumed, the better.

The results indicate that the compounds according to the present invention are stable in the presence of oxidizing biocides, at concentrations that are typical for cooling water systems. Therefore, they are of great use as tracers in cooling water systems, furthermore, apart from the inert fluorescent compounds of the present invention, no other compounds are known which exhibit an excitation above 380 nm which are also stable in the presence of oxidizing biocides.

The specific examples presented herein may be considered to be primarily illustrative. Various changes beyond those described will, without doubt, occur to the person skilled in the art; and such changes will be understood to form a part of this invention so long as they fall within the spirit and scope of the appended claims.

Claims (9)

1. Fluorescent compound of formula: characterized in that Ri and R2 are either both SO3M or one of Ri and R2 is SO3M and the other is COOM, where M is selected from the group consisting of H, Na, K, Rb, Cs, Li or ammonium. 2. Method for the preparation of a fluorescent compound of formula: characterized in that Ri and R2 are either both SO3M or one of Ri and R2 is SO3M and the other is COOM, where M is selected from the group consisting of H, Na, K, Rb, Cs, Li or ammonium, which includes condensing a 1,8-naphthalic anhydride with formula: with an o-phenylenediamine of formula: where Ri and R2 are as previously defined. 3. Process for preparing compounds of formula I: characterized in that Ri and R2 are either both SO3M, or one of Ri and R2 is SO3M and the other is COOM, where M is selected from the group consisting of H, Na, K, Rb, Cs, Li or ammonium, by condensing o -amino-nitro aromatics with the formula where Ri is as previously defined, with the appropriate 1,8-naphthalic anhydride characterized in that R2 is as previously defined, wherein such condensation is carried out in such a way that in situ reduction of the nitro group is achieved with a suitable reducing agent. 4. Application of a compound of formula: wherein Ri and R2 are either both SO3M, or one of Ri and R2 is SO3M and the other is COOM, wherein M is selected from the group consisting of H, Na, K, Rb, Cs, Li or ammonium, as an inert fluorescent tracer in an industrial water system. 5. A compound according to any one of claims 1-4 in which R1 and R2 are both SO3M. 6. A compound according to any one of claims 1-4 in which R 1 is SO 3 M and R 2 is COOM. 7. A compound according to any one of claims 1-4 in which R 1 is COOM and R 2 is SO 3 M. 8. Application according to claim 4, in which the industrial water system is a cooling tower. 9. Use according to claim 4, wherein the concentration of the fluorescent compound in the industrial water system is at least 0.01 ppb and not more than 10 ppm.